The relationship between the average number of prey eaten by each predator per unit time vs. prey density

Numerical Response

The increase in the number of predators by reproduction and immigration with increases in the prey population

Type I Functional Response

Explanation: Each individual predator takes a fixed fraction of the prey population each time period. If prey density double, the number each predator eats per day doubles Assumptions

Assumptions: Encounter and kill rate is simple fraction of prey population, V No “saturation” or “satiation” of predator No “handling” or “processing” time No “switching” from one prey species to another

Biological Basis: Likely valid for the lower range of prey densities for some species

Type II Functional Response

Explanation: “Saturating functional response” As prey density increases, the number of prey each predator eats per day reaches a constant number.

Assumptions: Encounter rate initially limits predation, but processing/handling time (including digestion) or satiation eventually limits food intake No “switching” from one prey species to another

Biological Basis: Likely applies to most predators, and a nearly Type I response occurs over lower range of prey density.